Many processes in biological or medical research such as enzymatic catalyzed reactions or cell culture require ambient temperatures between 25 and 45° C. Higher temperatures of up to 70° C. are needed to denaturate proteins or kill pathogenic organisms. Since nearly all biological processes are performed in this temperature range, heating devices for laboratory vessels are commonly used in biological laboratories and are available for many different applications or vessels.
For biological research, the most common laboratory vessel is a so called “tube”, i.e. tube-shaped, cylindrical vessels as shown in FIG. 1 with a screw cap 20, mostly made from polymers such as polyethylene or polypropylene. Such tubes have usually a capacity of 1 to 200 ml and can be heated up to autoclave temperature (about 130° C.) for sterilizing or cooled as low as −70° C. for storage purposes. Tubes are disposable and can be obtained from several companies.
Heating devices for biological research, especially for tubes, are commercially available and comprise often a rack having a plurality of openings for tubes and a heating or warming dry block. The temperature is usually maintained by electrical resistance heating and can be controlled very precisely in order to perform temperature-dependent reactions.
For example, German patent publication DE 19646114 A1 discloses a laboratory thermostat with heating blocks and a holder for a plurality of tubes. Patent Publications WO 2004/018105 and US 2008/0182301 describe heating devices for a plurality of samples, wherein the tubes are located in a sample block which is pressed on the heating block with a clamp-like lid to ensure good transfer of heat between the samples, the sample block and the heating block.
Heating devices with heating blocks are capable of heating many tubes at the same time to the same temperature. However, sometimes there is a need for processing an individual sample or a limited number of samples, but at different temperatures.
A heating device for a single laboratory vessel is disclosed in US 2006013064 A1. Here, heating a mixing device for a laboratory vessel with a heat conducting drive axle is described. However, this heating device requires a special mixing vessel and cannot be used for the commonly used tubes since the heat is applied through the drive axle of the mixer.
U.S. Pat. No. 3,737,627 describes an electric test tube heater wherein individual laboratory tubes can be heated. The laboratory tube is inserted in the heating circuit and fixed with a clamp. Since the tube is only inserted into the heating circuit (with some play) and the heating circuit is separate from the clamp, the tube is not well encompassed by the heating circuit, resulting in poor regulated transfer of heat.
In the heating device according to European Patent EP 0826420, the laboratory tube is fixed in a bushing with an integrated heating circuit with a screw. Inserting and removing a laboratory tube from such a device is laborious and requires a screw driver.
Accordingly, there is a need for a heating device, suitable for the heating of laboratory vessels to temperatures common in biological research. The heating device should be easy and safe to handle, space saving and compatible with other lab equipment.